Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual era o oponente no Estádio Arrowhead?
 ###Tabelas: CREATE TABLE top_appearances_in_uefa_club_competitions (top_appearances_in_uefa_club_competitions_id AUTO_INCREMENT PRIMARY KEY, Rank INT, Player VARCHAR, Games INT, Goals INT, Goal Ratio INT, Debut in Europe INT) CREATE TABLE democratic_primary (democratic_primary_id AUTO_INCREMENT PRIMARY KEY, Poll source VARCHAR, Dates administered VARCHAR, Roy Barnes VARCHAR, Thurbert Baker VARCHAR, DuBose Porter VARCHAR, David Poythress VARCHAR, Undecided VARCHAR) CREATE TABLE regular_season (regular_season_id AUTO_INCREMENT PRIMARY KEY, Week INT, Date VARCHAR, Time VARCHAR, Opponent VARCHAR, Result VARCHAR, Game site VARCHAR, NFL Recap VARCHAR, Record VARCHAR) CREATE TABLE team_variations_across_different_versions (team_variations_across_different_versions_id AUTO_INCREMENT PRIMARY KEY, Gatchaman VARCHAR, Eagle Riders VARCHAR, Rank VARCHAR, Bird Uniform VARCHAR, Weapon VARCHAR, Mecha VARCHAR, Japanese voice actor VARCHAR, Voice actor (Eagle Riders) VARCHAR) CREATE TABLE made_the_cut (made_the_cut_id AUTO_INCREMENT PRIMARY KEY, Player VARCHAR, Country VARCHAR, Year(s) won VARCHAR, Total INT, To par VARCHAR, Finish VARCHAR)  
SELECT Opponent FROM regular_season WHERE Game site = arrowhead stadium